A method and a device for driving an electromagnetic load are described in German Patent No. 197 01 471. There, a method and a device are described for controlling solenoid valves that control the injection of fuel in an internal combustion engine. In particular, a so-called Common Rail System, driven by a solenoid valve, is described. Usually, for an accelerated switching on of the injectors, a so-called booster capacitor is used, which is charged at a voltage that is increased in comparison to the supply voltage. The capacitor is usually charged in a so-called Rapid Quenching Phase between two firings. In longer decelerations (cut-off phases) of the engine, i.e., in phases in which there is no injection, the capacitor discharges. The consequence of this is that in the next injection, the switching operation of the valve does not take place as rapidly as prescribed. To avoid this disadvantage, it is provided in the related art that after a longer pause between injections, the capacitor is charged before the next injection.
During recharging in the recharge phase, current flows through the load for a brief time such that the load in normal operation does not respond. The voltage induced by an interruption of the flow of current acts to charge the capacitor. In this context, under unfavorable conditions, it can happen that the load responds and a small quantity of fuel is metered out.
In devices of this type, the injectors must reliably be prevented from metering out any fuel in operating states in which no injection is called for, i.e., if the internal combustion engine is to be switched off.
On the basis of the mode of operation according to the present invention, it is possible to achieve increased safety in controlling the fuel injection. It is especially advantageous that the safety device can also be checked.